Group Selection Harvest Research Articles

Residual Stand Structure and Topography Predict Initial Survival and Animal Browsing of Redwood and Douglas-Fir Seedlings Planted in Coastal Forests of Northern California

Successful regeneration of commercial species is central to the long-term sustainability of forests managed for wood production. We studied two species of tree seedlings planted after group selection and single-tree selection harvesting in a 20 ha replicated silviculture experiment in stands dominated by coast redwood (Sequoia sempervirens (D.Don) Endl.). Treatments consisted of complete harvest in 1 ha group selection opening (GS), low-density dispersed retention (LD), aggregated high-density retention (HA), and dispersed high-density retention (HD). One year after planting, seedlings planted on a southwest aspect had the lowest survival rate, while northeast aspects had nearly complete survival rates. As expected, redwood had a higher survival rate than coast Douglas-fir (Pseudotsuga menziesii var menziesii (Mirb.) Franco). Survival rates exhibited a rise-peak-fall pattern with stand density, most notably on southwest-facing slopes, ranking LD > HA ≈ HD > GS treatments. Deer browsing of planted seedlings was a pervasive problem where Douglas-fir were preferentially browsed over redwood. In treatments with higher retention densities, browsing was less likely, ranking GS > LD > HA > HD treatments. Further from watercourses at higher elevation, the probability of browsing diminished. Overall, dispersed treatments outperformed aggregated and GS treatments by simultaneously maximizing survival and minimizing browsing of planted seedlings. We did not perform site preparation or herbicide treatment of re-sprouting hardwoods following harvest, and therefore recommend testing the effectiveness of understory vegetation management to enhance seedling survival. Consideration could also be given to planting more seedlings in anticipation of lower survival rates, and/or implementing seedling protection measures when and where heavy browsing is expected.

Tree regeneration and spatial patterning among midtolerant tree species following gap-based harvesting in a temperate hardwood forest

IntroductionField experiments of gap-based harvest systems in temperate northern hardwood forests have provided inconsistent support for the theory that such regeneration approaches can improve regeneration success among increasingly underrepresented tree species intermediate in shade tolerance. We established a field experiment in Wisconsin, USA testing the long-term response of tree regeneration to group selection harvesting that created small (50 m2–D:H 0.32), medium (200 m2—D:H 0.64) and large (380 m2—D:H 0.88) gaps.Materials and methodsLight levels were modeled to test the assumption of resource heterogeneity within and across these gap sizes. Spatial statistics were used to assess whether the point patterns of saplings of several midtolerant tree species (Betula alleghaniensis, Carya cordiformis, Fraxinus spp.) mapped in harvest gaps provided evidence for partitioning across resource gradients 9 years post-harvest. Finally, we measured occurrence and height of all saplings within the harvest gaps to test the effects of gap size and deer exclusion fencing on the density and total height of shade-tolerant and midtolerant tree regeneration.Results and discussionLight levels progressively increased with gap size, varied by position within gaps, and provided significant evidence of resource heterogeneity. The complex light gradients formed both within and across the three gap sizes may partially explain the statistically significant clustering of Fraxinus spp. saplings in gap centers and north and east into the forested edge of medium and large gaps, C. cordiformis on the west sides of forested transitions surrounding large gaps, and B. alleghaniensis in the centers of large gaps. Densities of tolerant and midtolerant saplings were similar in medium and large gaps after nine growing seasons, though tolerant saplings averaged two meters taller across all three gap sizes. Our results show that gap-based silvicultural systems can create resource gradients that are sufficient to regenerate mixtures of species with high to intermediate tolerance of shade. However, prescriptions beyond harvesting and deer exclusion fencing may be necessary for the recruitment of midtolerant species to canopy positions.

The influence of forest management practices on seasonal bat species occurrence and activity at the Kisatchie National Forest in Louisiana, USA

In the southeastern United States, where forests are the primary land cover type, understanding how forest stand characteristics and forest management practices influence bat distributions is critical for bat conservation and management. We deployed passive acoustic monitors to record bat calls at sites representing six forest types at the Kisatchie National Forest in central Louisiana during two winter (January–February 2020 and December 2020–February 2021) and two summer (June–August 2020 and 2021) periods. We also collected environmental data at the landscape and local scales to help explain patterns in bat species occurrence. We detected big brown bats (Eptesicus fuscus), eastern red/Seminole bats (Lasiurus borealis/L. seminolus), Myotis species, tricolored bats (Perimyotis subflavus), Mexican free-tailed bats (Tadarida brasiliensis), and hoary bats (Aeorestes cinereus) during both periods, and additionally detected evening bats (Nycticeius humeralis) during the summer. We observed seasonal differences in habitat use, and found that three bat species were more active during the summer in pine forests with group selection harvest, pine forests managed for red-cockaded woodpeckers (Leuconotopicus borealis), and pine forests that were clearcut within five years of our study when compared to unmanaged pine forests, thinned pine forests, and bottomland hardwood forests. Contrary to other studies, we found that the predicted probability of occupancy decreased with increasing proximity to riparian areas for four bat species, which could reflect the complex understory vegetation conditions that we observed along the riparian corridors in our study area. Our research identified forest characteristics and management practices that promote bat species diversity and activity in central Louisiana and demonstrated that pine forests with open understories and small openings in the canopy provide important foraging habitat for bats that occur in our study area and possibly other regions in the southeast.

Deadwood Reduces the Variation in Soil Microbial Communities Caused by Experimental Forest Gaps

Downed woody debris (DWD) creates heterogeneous microsites that are beneficial to enhancing biodiversity and that represent persistent nutrient and carbon pools. Windthrow events characteristic of northern deciduous forests naturally produce abundant DWD and canopy openings that enhance structural complexity, but group selection harvesting reduces DWD biomass despite promoting vertical structural complexity. We implemented a field experiment to test the response of the soil microbial community (SMC) to DWD addition in created gap openings to compare experimental windfall to group selection harvest. Our objective was to assess the variability among microbial functional groups within canopy openings versus at the stand scale with DWD addition four- and five-year posttreatment. This study builds on previous studies at the Flambeau Experimental Research Site (Wisconsin, USA) that tested the effects of canopy openings alone on the SMC abundance and soil respiration along the gap gradient. Soils were sampled in four treatments (gaps, gaps + DWD addition, control + DWD addition and a control), and SMC abundance and composition were quantified using a modified phospholipid fatty acid (PLFA) and fatty acid methyl ester (FAME) method. Our analyses indicated a stronger response of the SMC to within-gap microenvironments than to the stand-level interaction of DWD addition and canopy openings. We found significant variation in the SMC along the north–south transect within the gaps, with higher abundance of arbuscular mycorrhizal fungi, soil temperature, unsaturation bacterial stress ratio and lower bacterial abundance in the northern portion of the canopy openings. DWD addition within gaps buffered the soil from extreme temperature changes while increasing gram-positive bacteria abundance that tend to rely on recalcitrant carbon sources and are more resistant to environmental stress. These patterns indicate that gap openings and DWD addition increased soil microenvironmental spatial heterogeneity and suggest that structural complexity may contribute to carbon storage by promoting sequestration in regenerating vegetation and by shaping the SMC to favor greater C use efficiency.

Long-term effects of alternative partial harvesting methods on the woody regeneration layer in high-elevation Quercus rubra forests of the southern Appalachian Mountains, USA

High-elevation Quercus rubra forests in the Appalachian Mountains represent a transition zone between temperate mixed-Quercus forests that dominate lower elevations (<1350 m) and Picea-Abies forests at high (>1530 m) elevations. Little information exists specific to the response to disturbance, including timber harvesting, in these forests. In this study, we examined the long-term (22 years) effects of alternative regeneration methods – group selection harvests (GSH) and shelterwood with high (SWH; 9.0 m2/ha) and low (SWL; 5.0 m2/ha) residual basal area, and undisturbed control (CON) – on the development of the regeneration layer in high-elevation Q. rubra forests in the Appalachian Mountains. Treatments affected the density of the regeneration layer (stems ha−1; SPH), but results varied by species group. Density of Q. rubra saplings (stems ≥ 3.8 cm dbh and <10.9 cm dbh) was significantly greater in GSH (250 SPH), SWH (85 SPH), and SWL (121 SPH) than CON (0 SPH). For shade-tolerant species, density averaged 1095 SPH in SWH and SWL and was significantly greater than in CON. Shade-tolerant Acer rubrum was the most abundant species in the sapling layer 22 years post-harvest. Survival of individuals tagged and followed over time was unaffected by treatment, however, height of Quercus seedlings was greatest in treatments with lower residual basal area (GSH and SWL). At Y22, the relatively low density of successfully regenerated Quercus stems in the regenerated stands suggests that additional treatments, including crown-touch release and/or prescribed burning, may be necessary to secure the continued recruitment of Quercus in these high-elevation Q. rubra forests.

Group selection silviculture for converting pine plantations to uneven-aged stands

Recent years have witnessed an increased interest in managing and restoring southern pine stands using uneven-aged silvicultural strategies, that rely on natural regeneration. Group selection harvests are regarded as an effective approach to induce natural regeneration and convert pine plantations to uneven-aged stands. In a wet flatwoods site in north-west Florida, we characterized natural regeneration (density, size, spatial distribution, hot spots) of slash pine (Pinus elliottii Englm.) eight years following group selection harvests and one year following prescribed fire in mature slash pine plantations. Our study utilized a long-term, operational scale experiment consisting of circular harvest group openings of four different sizes (0.1, 0.2, 0.4, 0.8 ha), each replicated three times. In all group openings, we stem mapped all regeneration > 1.37 m in height and measured their diameter at breast height (dbh) and total height. We also estimated understory shrub cover in the group openings. Overall, slash pine regeneration response was highly variable across group opening sizes and ranged between 150 (in 0.1 ha group openings) to 670 stems ha−1 (in 0.8 ha group openings). On average, 468 ± 105 (mean ± standard error) stems ha−1 were found in the group openings. Group opening size had no significant effect on regeneration density or size (ɑ =0.05). Position within group opening, however, had a significant effect on regeneration density and height, with higher density occurring in group opening centers and taller stems in northern positions. Shrub cover decreased with increasing group opening size and was lowest in northern positions. Dense shrub cover (60–100%) was associated with greater regeneration density. The areas with dense shrub cover appeared to have escaped prescribed fire and experienced lower seedling mortality. Spatial point pattern analysis showed aggregation of regeneration for all group sizes across all distances. Regeneration hotspots were mostly central and southern positions in group openings. Earlier observations of our study suggest that the group selection harvesting may be a suitable approach to regenerate slash pine and add an age-class (regeneration cohort) to even-aged stands in wet flatwoods sites.

Regeneration responses in black ash (Fraxinus nigra) wetlands: implications for forest diversification to address emerald ash borer (Agrilus planipennis)

Emerald ash borer (EAB) (Agrilus planipennis) has had an extensive impact across North America. It is currently present in Minnesota, USA but has not been observed in northern portions of the state where the vast majority of black ash (Fraxinus nigra) trees are located. Unlike other ash forest communities, the black ash forest type occurs in wetlands and is dominated by black ash with few associate species. Because of this, the loss of black ash can result in changes to the hydrological regime and species composition. The goal of this study was to quantify the structure and composition of regeneration 5 to 11 years post-harvest in three silvicultural systems (group selection, clearcut, and diameter-limit harvesting) to evaluate the potential for establishment of other tree species. Overall, regeneration post-harvest was high but variable across all systems. Across silvicultural systems, there was no significant relationships between residual overstory trees (> 10 cm dbh) basal area and non-ash regeneration TPH, indicating flexibility in designing treatments for diversification. Populus sapling (2.54–10 cm) density was significantly negatively correlated to the depth of the soil muck layer. In contrast, a positive relationship was observed between depth of the soil muck and black ash saplings. These findings indicate that specific silvicultural systems in combination with site quality (e.g., clearcuts on high-quality sites with shallow muck layers) may help to promote non-ash species in black ash forests that are threatened with EAB.

The Influence of Old and New Machines on Productivity and Costs of Four Yarding Methods in Small-Scale Forestry in a Maine Forest

Small forest landowners and loggers require information on the cost and productivity of available timber harvesting systems in order to make the best equipment allocation decisions, especially when the current generation of highly productive, capital-intensive harvesting machinery is well suited for clearcutting in large stands. Conversely, small-scale equipment is becoming more readily available that can help minimize the capital and operating costs associated with partial cuts and intermediate stand treatments or when operating in small-scale forests. The present study evaluated the productivity and yardings costs of four different yarding systems for old machines—a farm tractor, bulldozer, cable-skidder and forwarder—working in a group selection harvest of a mixed hardwood stand in the state of Maine, USA. A sensitivity analysis using the break-even technique and considering the same harvesting productivity and machines brands and models was used in this study to assess study differences between yarding machines costs in two different scenarios: old and new machines. Results indicate that the total machine and yarding costs for old machines were lower than for the new machines. For old machines, the yarding cost per unit delivered to the landing was lowest for the forwarder method ($2.34/m3) and highest for the cable-skidder method ($4.46/m3). In the case of new machines, the yarding cost per unit was lowest for the forwarder method ($3.95/m3) and highest for the cable-skidder method ($9.46/m3). The older machines might be a better option than new machines, particularly for small landowners who need to harvest small areas with low levels of harvesting.

Seedling development and regeneration success after 10 years following group selection harvesting in a sessile oak (Quercus petraea [Mattuschka] Liebl.) stand

This study showed that regeneration success (presence of oaks ≥ 150 cm in total height) in artificial canopy openings of a mature mixed sessile oak stand was mainly driven by initial oak seedling density. Small-scale harvesting methods as practiced in close-to-nature forestry may disadvantage the regeneration of more light-demanding tree species including sessile oak (Quercus petraea [Mattuschka] Liebl.) and thus cause regeneration failure. However, owing to the short-term nature of many previous studies, regeneration success of sessile oak could not be properly ascertained. This study examined oak seedling development over a time period of ten growing seasons in canopy openings of 0.05 to 0.2 ha in size created through group selection harvesting in a mature mixed sessile oak forest in southwestern Germany. We tried to answer the following research questions: (i) how do initial stand conditions relate to and interact with oak seedling density and seedling height growth, and (ii) what are the driving factors of regeneration success under the encountered site conditions. We evaluated the influence of solar radiation, Rubus spp. cover, initial oak seedling density, and competition from other tree species on change in density and height of oak seedlings, as well as overall regeneration success (oak seedlings ≥ 150 cm in height). Regeneration success increased with initial oak seedling density and solar radiation levels and decreased with early Rubus spp. cover. Density and maximum height of oak seedlings was negatively related with competition of other woody species. Results of our longer-term study demonstrate that forest management activities to regenerate sessile oak naturally are only successful in stands (i) without advance regeneration of other woody species and without established, recalcitrant ground vegetation, (ii) with a sufficiently high initial oak seedling density in larger patches following mast years, and (iii) where periodic monitoring and control of competing woody individuals can be ensured. Our findings further corroborate the view that natural regeneration of sessile oak in small-scale canopy openings is possible in principle.

Group selection harvesting supports diversity of forest specialist carabids

Increased fragmentation and considerable environmental changes in native forests caused by the timber-oriented forest managements are threatening the biodiversity of forests. As a remediation, uneven-aged approach is recommended during forest management, because this is less intensive and could be less harmful than even-aged practices. We tested the effects of clear-cutting (as even-aged method) and group selection harvesting (as uneven-aged method) on carabids in lowland oak forests. Pitfall traps and litter sifting were used during the study. We found that the total number of species was significantly higher in the gaps harvested by group selection and in the clear-cut than in the mature forests (control area). The species richness of forest specialist species was significantly lower in the clear-cuts than in the other area. Our findings demonstrated that the conventional clear-cutting caused a decrease in the number of forest specialist species. Therefore, group selection method should be favoured during forest management to maintain diversity.

Competition and tolerance of low soil water favor Carex dominance over establishing Acer seedlings in managed temperate mesic forests

Carex pensylvanica (Pennsylvania sedge) dominance of managed temperate mesic forest understories is associated with high deer browsing pressure, frequent partial timber harvests, invasive earthworms, and low seedling-to-sapling recruitment rates of canopy-dominant Acer saccharum (sugar maple). There is concern that Carex dominance may be difficult to reverse because Carex may decrease soil resource availability and tolerate these conditions better than Acer seedlings. However, evaluation of this notion and of management aimed at reducing possible Carex impacts on Acer seedlings is lacking. Here, we examine the effects of (1) removing Carex on soil water and the growth and survival of naturally-established Acer seedlings over a forest understory light gradient, (2) drought on growth, survival, water relations, and soil mineral N pools of potted monocultures and mixtures of Carex and Acer seedlings, and (3) summer vs. autumn glyphosate herbicide treatments on Carex and Acer seedling dynamics in group-selection harvest openings. Carex removal increased soil water and growth of naturally established Acer seedlings but only in harvest gaps >8% light. Carex exhibited greater tolerance of drought than Acer by closing stomates at lower pre-dawn water potentials (−4.2 MPa vs. −3.0 MPa), and incurring lower post-drought mortality (~0% vs. 50%). In well-watered Carex-Acer mixtures, Carex reduced soil NH4+ but not Acer growth or survival relative to Acer monocultures. Glyphosate treatments reduced Carex by >90%, but possible benefits to young Acer seedlings may have been offset by greater deer herbivory on Acer in glyphosate treatments. Our results indicate that Carex reinforces its dominance of mesic hardwood forest understories via water competition and drought tolerance mechanisms that slow the establishment and recruitment of canopy dominant Acer. These effects could be exacerbated by increased intensity and frequency of droughts in the future, such that Carex dominance of understories could accelerate the xerophication of these systems in the face of climate change. Herbicides can be used to reduce Carex but may need to be combined with deer population reductions to promote adequate Acer seedling to sapling recruitment for sustainable management by selection silviculture. The sustainability of other temperate mesic forests globally characterized by high ungulate populations and associated high graminoid density may be similarly challenged.

Can group selection with legacy retention change compositional trajectories in conventionally managed hardwoods?

Group selection has been proposed as a complementary system to conventional, uneven-aged management in temperate hardwoods (i.e. single-tree selection) to counteract declines in overstory diversity and growing importance of shade-tolerant species caused largely by past management activities. Mixed results from experimental group selection harvests in eastern North America and growing interest in retention forestry have led some scientists and managers to apply ideas from retention forestry into group selection systems. The Yellow Birch Legacy-Tree Project is a group selection experiment established in 2003, which incorporates single, dominant/co-dominant yellow birch (Betula alleghaniensis Britt.) legacy-trees into the centers of harvested canopy gaps in a northern hardwoods forest in the Upper Peninsula of Michigan. Group selection openings (n = 49) in three size classes based upon radii—small (11 m, n = 16), medium (16.5 m, n = 17), and large (22 m, n = 16)—were surveyed alongside single-tree selection reference sites (n = 20) 15 years post-harvest. Our goals were to (1) examine long-term trends in seedling and sapling abundance and diversity, (2) evaluate the initial and contemporary effects of gap size on regeneration, and (3) assess the overall efficacy of group-selection with legacy-tree retention in regenerating mid-tolerant and intolerant species, especially yellow birch. At 15 years post-harvest, we found that shade-tolerant sugar maple (Acer saccharum Marsh.) dominated regeneration layers across all treatments, but we observed modest increases in seedling and sapling diversity within openings that may alter long-term canopy composition over several cutting cycles. We found that gains in diversity and evenness in canopy gaps persisted through time and that large gaps (22 m radius) had the most species-rich and diverse regeneration compared to reference sites. Canopy gaps contained significantly higher densities of shade-intolerant and mid-tolerant seedlings and saplings compared to reference sites, namely red maple (Acer rubrum L.), black cherry (Prunus serotina Ehrh.), and yellow birch; however, most diversity occurred in shorter height classes. Nevertheless, legacy retention within group selection systems holds promise for maintaining ecological memory and structural complexity through time, but further treatments such as scarification may be necessary to shift compositional trajectories in favor of shade-intolerant and mid-tolerant species.

Bee Communities across Gap, Edge, and Closed-Canopy Microsites in Forest Stands with Group Selection Openings

AbstractAs insect pollinator populations continue to decline, it is essential to understand the impacts of anthropogenic activities, including forest management, on pollinator communities. Although multiple studies have shown that clearcutting is beneficial for bees, other less intense, selective silvicultural methods that result in disproportionate increases in edge habitat within stands are less well understood. We investigated bee community characteristics across microsites (center of cut, edge of cut, and closed-canopy forest) in three mixed-mesophytic forest stands subjected to group selection cuttings. Results revealed bee communities in the center of cuts and their edges to differ from those in forest microsites, and their diversity measures were higher than in forest microsites. Within-stand edge microsites did not differ from their cut centers in terms of their communities or their diversity. Finally, center of cut and edge microsites combined, and forest microsites, were characterized by different indicator species, thereby exemplifying differences between these two microsite groupings. These results suggest that group selection harvests support differing communities of bees across microsites and sustain a wide range of bee species, and that edges within these forest stands behaved more like extensions of canopy gap openings despite differences in forest physiognomy.

Group-selection silviculture conditionally enhances recruitment of yellow birch in a shade-tolerant hardwood forest

Wide-spread use of single-tree harvest methods has inhibited regeneration of yellow birch in shade-tolerant hardwood forests. Shelterwood harvesting can improve recruitment, but incurs higher costs, longer harvesting cycles, and produces an even-aged structure. Group selection (GS) harvesting provides an alternative method with the benefits of single-tree selection (STS; mixed-ages, shorter cycles), yet produces larger gaps that may favour recruitment of mid/intolerant tree species. Recent GS trial studies have shown promise, but results vary and differences in edaphic conditions and competition dynamics associated with climate, historical management, and season of harvesting may influence responses. We evaluated the yellow birch recruitment efficacy of GS in an Ontario shade-tolerant hardwood forest by comparing change in regeneration as percent ground cover (stems <50 cm) and large stem density (>50 cm) over ten years in STS harvested and unharvested forest relative to two types of GS gaps: “typical” gaps placed in suitable microsites, and indiscriminate “systematic” interval gaps harvested on a grid.Autumn-harvested gaps established 2–4× more yellow birch cover and recruited 7–10× more large stems by year ten than STS and winter harvested gaps; unharvested controls remained unchanged. Typical gaps recruited 3× more stems than systematic gaps in autumn-only. Soil disturbance and seed tree proximity were correlated to establishment of yellow birch cover in year 1, which predicted large stem recruitment by year 10. Winter-harvesting favoured sugar maple cover in year 1, which predicted lower yellow birch recruitment by year 10. These results indicate that autumn-harvested typical gaps optimised germination and growth conditions for yellow birch (light availability, soil disturbance, reduced competition, seed proximity/dispersal). Consequently, GS harvesting in autumn can be considered an effective alternative to shelterwood harvesting for yellow birch recruitment in poorly-represented shade-tolerant hardwood stands.

Bird Diversity as a Support Decision Tool for Sustainable Management in Temperate Forested Floodplain Landscapes

Sustainably managed forests provide multiple ecosystem services in cultural landscapes, including maintaining biodiversity. Better understanding of the benefits regarding the biodiversity of different silvicultural practices is important for sustainable landscape management. Conservation targets in forested landscapes should be determined by land managers and policy-makers, based on serious ecological research. This study deals with response of bird diversity to three different habitat types of temperate hardwood floodplain forests, which reflect specific forms of forest management. Research was based on long-term field bird census in the years 1998 to 2002 applying the point count method. Data was analysed using regression analysis with dummy variables. The results of the study indicate that hardwood floodplain forest heterogeneity, supported by different types of forest management (old-growth forest protection, group-selection harvesting and forest edge protection), provides large-scale habitat mosaic conditions suitable for many breeding bird species with different ecological niches. This result suggests that comparison of bird diversity response to different forest management types can be used as a decision support tool for sustainable landscape management strategy and local management practices in forested cultural lowland landscapes. Improvements in both regional and local ecological knowledge are generally needed in order to control floodplain land use decisions, which are typically made on the scale of landscape management.

Ungulate exclusion accentuates increases in woody species richness and abundance with canopy gap creation in a temperate hardwood forest

Forest biodiversity is declining due to a wide variety of anthropogenic factors. Forest and wildlife management can be part of the problem or part of the solution. Our objective was to examine the influence of white-tailed deer exclusion on the response of understory communities to a gradient in overstory disturbance. We expected that greater overstory disturbance would act synergistically with deer exclusion to increase understory species richness and abundance. In northern Wisconsin, USA, we monitored changes in understory vegetation in a temperate hardwood forest following four overstory treatments (no-harvest controls and three gap sizes) and two deer treatments (deer access or exclosure). By the seventh year following gap creation, understory species richness and the abundance of multiple species groups had increased, especially when deer were excluded. Effects were most pronounced in larger gaps, particularly among saplings of less shade-tolerant tree species. The tree seedling community responded similarly, but less strongly, to treatments. In contrast, change in the short-stature shrub and herbaceous community seven years following gap and deer treatments was limited and species-specific. Environmental conditions at the groundlayer, such as light availability and soil moisture content, rarely differed by treatment in our study. Increased density of understory vegetation at seven years post-treatment may have negated early pulses in resource availability resulting from gap creation. Gap creation alone increased species richness and abundance of woody taxa, whereas deer exclusion alone had little effect on the understory community. When treatments were applied in combination, we saw the greatest change in the plant community. Our study provides evidence that, when accompanied by a reduction in deer population density, relatively intense overstory disturbance (e.g., group-selection harvest) may be an effective management strategy for restoring forest heterogeneity.

Effects of conversion harvests on light regimes in a southern pine ecosystem in transition from intensively managed plantations to uneven-aged stands

Uneven-aged silviculture is increasingly viewed as ecologically and economically appropriate strategy to manage forest ecosystems. Consequently, there is interest in converting intensively managed pine plantations to uneven-aged stands in the southeastern United States. Understanding biophysical factors that determine performance and growth of desirable species is critical to success of such conversions. We initiated a replicated, long-term, operational-scale stand conversion experiment in mature slash pine (Pinus elliottii Engelm.) plantations in mesic-wet flatwoods sites in northwest Florida, and examined how five conversion harvests (shelterwood, group selection, staggered third row thin, third row thin, cut 2 leave 3 thin harvests), in addition to an uncut control, affected understory light availability in these forests. Light availability was measured in terms of leaf area index, sky, and fractions of Absorbed Photosynthetically Active Radiation (both direct and diffuse). The values of these variables were derived by analyzing a total of 880 (450 in the harvest treatment plots and additional 430 in the gaps of group selection) Digital Hemispherical Photographs using image analyzing software CAN-EYE. We found that shelterwood harvest resulted in highest light availability, whereas greatest variability in light conditions was observed following group selection harvests. Among the four circular gap sizes (0.1, 0.2, 0.4 and 0.8 ha) we studied, gaps of larger sizes had greater light availability. Light availability increased as the distance from the gap edge increased and was highest either in the center of the gap or slightly towards northern and western sides of the gap center. Variability in light availability increased as gap size increased from 0.1 to 0.4 ha but was reduced in the 0.8 ha gap. In shade-intolerant species like slash pine in wet flatwoods-- where soil moisture and nutrients are generally not limiting-- light availability could be the most critical factor determining the success of regeneration and stand conversion. Overall, the results indicated that shelterwood harvest resulted in highest average light availability which would be conducive to slash pine regeneration while group selection harvest created the most diverse light environment during the stand conversion which may promote a broader diversity of groundcover species. Long-term monitoring of regeneration growth and recruitment following prescribed burning and over multiple cutting cycles will determine if slash pine can be sustainably managed using uneven-aged silviculture.

Understory light predicts stump sprout growth in mixed multiaged stands in north coastal California

Regeneration of commercial species is central to long-term success of multiaged management for wood production. We examined relationships between understory light, varying overstory tree retention, and growth of coast redwood (Sequoia sempervirens; commercial species) and tanoak (Notholithocarpus densiflorus) stump sprouts initiated by group selection and single-tree selection harvesting in 80–100 year old mixed stands at four sites. Treatments included a complete harvest in 1-ha group selection openings, low-density dispersed retention, and either aggregated or dispersed high-density retention. Post-harvest stand density index and basal area were useful predictors of understory light. Mean and maximum understory light did not differ significantly between treatments with the same density where residual trees were retained in aggregated versus dispersed spatial patterns. However, the dispersed retention had lower minimum light levels when compared to the aggregated retention treatment. Aspect appeared to influence understory light more in dispersed treatments. At all light levels, the dominant sprout within clumps of redwood stump sprouts generally grew faster than dominant tanoak sprouts within tanoak sprout clumps. Differences in sprout height growth between aggregated and dispersed treatments were minimal. Stump size had a significant effect on redwood stump sprout height growth, with sprouts on the largest stumps growing approximately twice as quickly as sprouts on the smallest stumps. In the low density dispersed treatment, redwood sprouts outperformed tanoak sprouts by the greatest margin. Regeneration of redwood and tanoak was most rapid within group selection openings.

Area requirements and landscape‐level factors influencing shrubland birds

ABSTRACTDeclines in populations of birds that breed in disturbance‐dependent early‐successional forest have largely been ascribed to habitat loss. Clearcutting is an efficient and effective means for creating early‐successional vegetation; however, negative public perceptions of clearcutting and the small parcel size typical of private forested land in much of the eastern United States make this practice impractical in many situations. Group selection harvests, where groups of adjacent trees are removed from a mature forest matrix, may be more acceptable to the public and could provide habitat for shrubland birds. Although some shrubland bird species that occupy clearcuts are scarce or absent from smaller patches created by group selection, some of these smaller patches support shrubland species of conservation concern. The specific factors affecting shrubland bird occupancy of these smaller patches, such as habitat structure, patch area, and landscape context, are poorly understood. We sampled birds in forest openings ranging 0.02–1.29 ha to identify species‐specific minimum‐area habitat requirements and other factors affecting shrubland birds. We modeled bird occurrence in relation to microhabitat‐, patch‐, and landscape‐level variables using occupancy models. The minimum‐area requirements for black‐and‐white warblers (Mniotilta varia), common yellowthroats (Geothlypis trichas), chestnut‐sided warblers (Setophaga pensylvanica), eastern towhees (Pipilo erythrophthalmus), and gray catbirds (Dumetella carolinensis) were ≤0.23 ha, whereas indigo buntings (Passerina cyanea) and prairie warblers (S. discolor) required openings of 0.56 ha and 1.11 ha, respectively. Notably, prairie warblers were more likely to occur in openings closer to large patches of habitat such as powerline corridors, even if those openings were small in size. We concluded that, despite their inability to support the entire suite of shrubland species, small forest openings can provide habitat for several species of conservation concern if proper attention is given to promoting suitable microhabitat, patch, and landscape characteristics. © 2017 The Wildlife Society.

Factors affecting bee communities in forest openings and adjacent mature forest

Anthropogenic disturbance of habitat is considered a contributing factor of pollinator declines, but some disturbances such as silviculture, may have positive implications for pollinator communities. Silviculture is a key source of disturbance in the eastern USA and thus, developing a better understanding of its ramifications for these keystone species is important for effective ecosystem conservation. We sampled bees in 30 forest openings created by group selection harvest as well as 30 sites in adjacent mature forest to examine the extent to which small forest openings support bees, to identify environmental variables influencing bee abundance and diversity, and to gauge their potential to augment bee populations in adjacent unmanaged forest. Bees were significantly more abundant and diverse in forest openings than in mature forest, but species composition did not differ. There was no relationship between opening size and abundance or diversity of bees in openings or adjacent mature forest. Both abundance and diversity were generally positively related to the amount of early-successional habitat on the landscape. Within openings, overall abundance and diversity decreased with vegetation height and increased with a metric representing floral richness and abundance. Notably, social, soft-wood-nesting, and small bees exhibited the opposite pattern in adjacent forest, increasing with vegetation height in openings and decreasing with greater floral richness and abundance within openings. Our results suggest that the creation of small forest openings helps to promote bees both in openings and adjacent mature forest, but this pattern is not consistent for all guilds.